Inversion symmetries of time and space lead to the spin degeneracy of carriers
in a solid. In 2D systems confined to GaAs heterostructures and quantum
wells, the spatial inversion asymmetry resulting from the zincblende crystal
structure and/or the confinement potential lifts this degeneracy and can
result in measurable physical quantities. This presentation will cover our
experimental determination of the spin-splitting via Shubnikov-de Haas and
commensurability oscillations in high-mobility GaAs 2D holes and its
quantitative comparison with theretical calculations. We show that the
spin-splitting in this system is large and can be easily tuned via front- and
back-gates. We will also present data which suggest that the puzzling
"metallic" behavior recently observed in 2D systems may be related to the
spin-splitting.